1. Field of the Invention
The invention relates to an acoustic auditory aid for the rehabilitation of partial neurosensory hearing loss.
2. Description of the Related Art
At the present time, acoustic auditory aids available on the market are classified in two product categories: ear contour devices and intra-auricular devices.
Ear contour devices comprise a casing in the shape of an arc of a circle meant to be lodged behind the ear, this casing generally containing one or more sensors such as microphones, an energy source of the cell or battery type, and electronic circuits for analog and/or digital signal amplification and processing. The electronic circuits generate an acoustic signal that is sent into the auditory canal of the patient through an acoustic tube held in the auditory canal by an intra-auricular plug.
This intra-auricular plug, moreover, makes it possible to reduce acoustic Larsen phenomena between the earpiece and the point of sound emission.
Beyond the fact that the ear contour devices are standardized, these devices present great ease of implementation, high reliability and adequate performance characteristics, due in part to the relatively large available volume, making it possible to integrate all necessary electronic circuits. However, these devices present the disadvantage of being painful to wear, and of posing a threat of falling consequent to certain movements of the head. Moreover, they are relatively visible and lack esthetics. They do not make it possible to totally eliminate Larsen phenomena on account of the fact that the microphone is relatively close to the earpiece, which obliges them to be adjusted in a sub-amplification mode. In addition, the intra-auricular plug also presents disadvantages, in particular the disagreeable sensation of blocked up ear, perception of parasitical sounds during chewing, and problems of hygiene and potentially of infections, due to the fact that it plugs the auditory canal.
As far as the second category of devices available on the market is concerned, intra-auricular devices present themselves in the form of small casings meant to be inserted directly in the external auditory canal. This casing is made of a synthetic resin shell, whose shape is fitted by molding to the anatomy of the external auditory canal of each patient. This casing brings together, in a highly reduced volume, the sound sensor, the electronic signal amplification and processing circuits, the earphone, the energy source (electric cell). Compared to the ear contour devices, they present the advantage of being notably less visible and compact. On the other hand, they generate significant Larsen phenomena, both mechanical and acoustic, due to the proximity of the microphone and the earphone, which obliges them to be adjusted to a sub-amplification mode even lower than the ear contour devices. The miniaturization of the microphone and the earphone does not make it possible to obtain acoustic qualities of high quality.
Moreover, the low available volume makes difficult, indeed impossible, the addition of supplementary microphones or of more sophisticated signal processing functions. It presents low autonomy due to the use of an electric cell necessarily of small dimensions. On account of its small size, its manipulation, in particular during adjustments and battery changes, is difficult, which leads to risks of dropping during its withdrawal from the auditory canal. As with the ear contour devices, they cause disagreeable sensations of blocked up ear, raise hygiene problems, with risks of infection and premature wearout of the device.